Process for the preparation of monosodium glutamate

ABSTRACT

The invention provides a process for the preparation of monosodium glutamate from a fermentatively prepared solution containing monoammonium glutamate, the process comprising: a) contacting the solution containing monoammonium glutamate salt with a basic anion exchange resin of at least medium strength to split the salt, whereby glutamate anions attach to the anion exchanger and ammonia is released in the solution; b) subjecting the ammonia-containing solution to distillation, to recover volatile ammonia therefrom; c) contacting the glutamate-containing anion exchange resin with a sodium base solution to regenerate the basic anion exchanger and to directly form monosodium glutamate salt in solution; and d) crystallizing monosodium glutamate salt directly from the monosodium glutamate-containing solution, wherein the crystallized salt has a purity of at least 98%.

The present invention relates to a process for the preparation ofmonosodium glutamate (hereinafter referred to as MSG) from a glutamicacid fermentation broth.

More particularly, the present invention relates to a process for thepreparation of MSG from a fermentatively-prepared solution containingmonoammonium glutamate.

MSG is a well-known food additive which has been used for decades andwhich is used today mainly in the Far East, with a consumption of about800,000 tons annually. Because of the great demand for MSG, manyprocesses have been developed and/or proposed for the preparationthereof.

Thus, e.g., U.S. Pat. Nos. 2,877,160 and 2,978,384 teach variousfermentation processes for the production of glutamic acid; U.S. Pat.Nos. 2,773,001 and 2,947,666 teach such processes in conjunction withthe use of strong cation exchange resins to absorb glutamic acid, whichis then eluted with normal hydrochloric acid or with dilute ammoniumhydroxide, respectively.

In 1967, U.S. Pat. No. 3,325,539 was published, in which there wasdescribed and claimed a method for separating glutamic acid and saltsthereof from a fermentation broth containing the same and solidmaterials, which method comprises passing fermentation broth containingglutamic acid, salts thereof, and solid materials upflow through a bedof strongly acidic cation exchange resin on the hydrogen cycle at a ratesufficient to expand the bed between 1.05 and 1.6 times its originaldepth, thereby adsorbing glutamic acid on said resin; discontinuing theflow of fermentation broth over said resin; and eluting said adsorbedglutamic acid from said resin with a 0.5-2 N sodium hydroxide solution.

MSG production via adsorbing glutamic acid on an acidic cationexchanger, as suggested in U.S. Pat. No. 3,325,539, suffers from severaldisadvantages: (1) a high consumption of reagents, entailing productionof large amounts of by-product salts; (2) using an acidic cationexchanger frequently results in crystallization of glutamic acid on theresin material (column 3, lines 18-20); (3) the cation exchanger adsorbsthe glutamic acid as well as the cation bound to it, and the cationspresent as impurities in the fermentation liquor, mostly resulting fromthe carbohydrate feed. As a result, large volumes of the resin arerequired. In many cases, only about one-third of the total availablecation exchange capacity is available for glutamic acid adsorption.

The reactions involved with the process using acidic cation exchangersto adsorb glutamic acid (H₂ G) from an acidic solution and regenerationby a base are as follows:

    ______________________________________    (1) NH.sub.3 + H.sub.2 G + NH.sub.4 HG                                 Neutralization in                                 fermentation    (2) NH.sub.4 HG + 2R.sup.- H.sup.+  + R.sup.- NH.sub.4.sup.+  + R.sup.-        H.sub.3 G.sup.+    (3) R.sup.- H.sub.3 G.sup.+  + 2NaOH + R.sup.- Na.sup.+  + NaHG +        2H.sub.2 O    (4) R.sup.- Na.sup.+  + R.sup.- NH.sub.4.sup.+  + H.sub.2 SO.sub.4 +        2R.sup.- H.sup.+  +        1/2 Na.sub.2 SO.sub.4 + 1/2 (NH.sub.4).sub.2 SO.sub.4    (5) H.sub.2 G + 2NaOH + NH.sub.3 + H.sub.2 SO.sub.4 + NaHGA +        1/2 Na.sub.2 SO.sub.4 + 1/2 (NH.sub.4).sub.2 SO.sub.4    ______________________________________

Such a process doubles the consumption of extra base and acid values,and produces two equivalents of by-product salt per mole of the product.In fact, reagent consumption and by-product formation are even higher,as shown in U.S. Pat. No. 3,325,539. The MSG obtained in reaction (3)above is acidulated to pH=3.2 to crystallize the glutamic acid, which isthen neutralized.

Five years later, in 1972, U.S. Pat. No. 3,655,746 was published, whichdescribes the attempts to find a satisfactory process for producing MSG,as follows:

"Heretofore a number of processes have been proposed for the preparationof MSG from a glutamic acid fermentation broth, but those processesinvariably involve the steps of allowing glutamic acid hydrochloride,calcium glutamate, zinc glutamate, ammonium glutamate or glutamic acidto crystallize from the broth, then recovering those crystals andsubsequently neutralizing them with, for instance, sodium hydroxide orsodium carbonate to obtain MSG."

"Those processes not only require complicated steps, but also result inunsatisfactory yields. Aside from those processes, a process is known inwhich an organic solvent is used to directly allow MSG to crystallizefrom the broth, but the resulting crystals are so low in purity thatthey must require aftertreatment."

"While the conventional purification processes employing cation exchangeresin involve the adsorption and desorption of glutamic acid itself onand from resins, the resin in the present invention is employed for theadsorption of impurities, which makes it possible to purify by far agreater quantity of broth per unit volume of the resin."

With this background in mind, U.S. Pat. No. 3,655,746 teaches and claimsa process for producing MSG which comprises contacting a glutamic acidfermentation broth at a pH between about 5 and about 9 with an amount of1 liter by wet volume of a strongly basic anion exchange resin relativeto about 0.2 to 0.6 molecular equivalent at the anionic impuritiescontained in said broth; adding to the effluent from the resin astoichiometric amount of sodium hydroxide relative to the glutamic acidcontained therein; and recovering the crystals of MSG thus obtained.

As described in said patent, the resin is employed in an amount enoughto substantially adsorb the soluble impurities in the broth, but not insuch an excess as to adsorb glutamic acid itself.

U.S. Pat. No. 3,655,746 uses strongly basic anion exchangers to removesoluble anionic impurities and coloring matter from the fermentationliquor. However, cationic and neutral impurities, particularlynon-fermentables, are left with the glutamic acid and interfere in thecrystallization of pure MSG. As a result, "it is particularly suitablefor the treatment of broth which is low in the concentration ofimpurities other than organic acids." (column 4, lines 28-33).

Today, more than twenty years later, the major commercial processes forproducing MSG from a fermentation broth involve acidulation with amineral acid to a pH of about 3.2 to form the mineral acid salt,followed by crystallization of glutamic acid. Said glutamic acid is thenseparated, purified through recrystallization, and then reacted withsodium hydroxide to produce MSG.

However, even the commercial processes used today suffer from manydisadvantages and problems.

Thus, referring, e.g., to a known commercial process in which sulfuricacid is the mineral acid used, the reactions involved in the formationof MSG (NaHG) can be represented as follows:

    ______________________________________    (1)    NH.sub.3 + H.sub.2 G + NH.sub.4 HG                              Neutralization in                              fermentation    (6)    NH.sub.4 HGA + 1/2 H.sub.2 SO.sub.4 + H.sub.2 G +                              Acidulation           1/2 (NH.sub.4).sub.2 SO.sub.4    (7)    H.sub.2 G + NaOH + NaHGA                              Reacting the acid with                              NaOH    (8)    H.sub.2 G + NaOH + NH.sub.3 + 1/2 H.sub.2 SO.sub.4 + NaHG + 1/2           (NH.sub.4).sub.2 SO.sub.4    ______________________________________

Producing a mole of MSG consumes, in addition to the base required, onemole of ammonia and an equivalent of sulfuric acid, and forms anequivalent amount of the by-product ammonium sulfate.

Thus, the process uses up reagents and is therefore either wasteful orexpensive, since ammonium sulfate is not a high value fertilizer ordesired side product, and crystallization of ammonium sulfate isexpensive.

Secondly, the purity of the glutamic acid precipitating in acidulationby sulfuric acid is low. Recrystallization is required, involving inmany cases a phase transformation from α to β. These operations hold upcapacity, are expensive in energy consmption, and use reagents for pHadjustment. In addition, large recycles are involved, further increasingcapacity hold-up and reagent consumption.

Other disadvantages are related to the large volumes of ammonium sulfatesolutions formed: the glutamic acid solubility in these solutions ishigh enough to cause major product losses; and crystallization ofammonium sulfate from this solution requires large crystallizationcapacity, as well as consuming large amounts of energy.

In a process described in the recent Japanese Patent 94017346, thefermentation liquor is treated with sulfuric acid to precipitateglutamic acid at the isoelectric point. The mother liquor is acidifiedto pH 1.5 by adding 95% H₂ SO₄, and passed over a strongly acidic cationexchange resin to absorb glutamic acid. The absorbed glutamic acid iseluted with glutamic acid fermentation liquor containing urea, toprevent glutamic acid crystallization in the resin. The high consumptionof reagent acids and bases, and the formation of low or negative valueby-products, are not avoided, and an impurity addition is required. Thelatter entails the additional costs of a reagent and of urea removalfrom the product.

British Patent 811,688 and U.S. Pat. No. 2,921,002 recover glutamic acidfrom solutions comprising glutamic acid by absorption on anionexchangers. Said British patent describes a process for separating andconcentrating glutamic acid from an aqueous liquid containing the sameby a series of treatments with ion exchangers. First, cation and anionexchangers are used to remove cationic and anionic impurities,respectively. Then the glutamic acid is absorbed on a weakly basic anionexchanger and eluted by a strong acid solution. A base is added toadjust the pH to 3.2, and glutamic acid is crystallized.

With some adjustment, the above-described process seems applicable alsofor the preparation of monosodium glutamate from a fermentativelyprepared solution containing ammonium glutamate. The ammonia is boundfirst to a strongly acidic cation exchanger in its H form:

    ______________________________________    (1)    NH.sub.3 + H.sub.2 G + NH.sub.4 HG                                Neutralization in           fermentation    (9)    R.sup.- H.sup.+  + NH.sub.4 HG + R.sup.- NH.sub.4.sup.+  + H.sub.2           G    ______________________________________

The liberated glutamic acid is bound to a weakly basic anion exchanger:

    H.sub.2 G+R→R·H.sub.2 G                    (10)

and eluted with NaOH to form MSG-containing solution:

    R H.sub.2 G+NaOH→R+NaHG                             (11)

The strongly acidic cation exchanger is regenerated by a strong acid,e.g., HCl:

    R.sup.- NH.sub.4.sup.+ +HCl→R.sup.- H.sup.+ +NH.sub.4 Cl(12)

The over-all process is:

    H.sub.2 G+NH.sub.3 +NaOH+HCl→NaHG+NH.sub.4 Cl       (13)

This process consumes, per mole of MSG, a mole of ammonia and a mole ofHCl; it produces a mole of NH₄ Cl, a by-product of low or even negativevalue. Another disadvantage is the large volume to be processed, due tothe low solubility of glutamic acid.

British Patent 2,103,221 relates to the removal of glutamic acid from amixture of amino acids, using a strong anion exchange resin. However,said patent does not teach or suggest a commercial process for obtainingMSG of high purity.

With the above-described state of the art in mind, according to thepresent invention there is now provided a process for the preparation ofmonosodium glutamate from a fermentatively-prepared solution containingmonoammonium glutamate, said process comprising (a) contacting saidsolution containing monoammonium glutamate salt with a basic anionexchange resin of at least medium strength to split said salt, wherebyglutamate anions attach to said anion exchanger and ammonia is releasedin said solution; (b) subjecting said ammonia-containing solution todistillation, to recover volatile ammonia therefrom; (c) contacting saidglutamate-containing anion exchange resin with a sodium base solution toregenerate said basic anion exchanger and to directly form monosodiumglutamate salt in solution; and (d) crystallizing monosodium glutamatesalt directly from said monosodium glutamate-containing solution,wherein said crystallized salt has a purity of at least 98%.

The term "medium strength basic anion exchange resin," as used herein,is intended to denote resins having an apparent basicity in the range ofpKa of at least 8, preferably of at least 9, since it has been foundthat weakly basic anion exchangers having an apparent pKa of less than8, preferably less than 9, are not suitable for use in the presentinvention to split ammonium glutamate, attach the glutamate and releaseammonia.

As will be realized, the present process has many advantages over theprocesses of the prior art, both in cost and in efficiency.

As indicated above, as a result of step (a) there is obtained an anionexchange resin with glutamate attached thereto and a solution whichcontains the cation contaminants, the neutral contaminants, and ammonia.Since ammonia is the most volatile component of said solution, it iseasily recovered for recycling.

Thus, in preferred embodiments of the present invention, the ammoniarecovered by said distillation is recycled for the fermentativepreparation of monoammonium glutamate.

In the aforementioned especially-preferred embodiment of the invention,the process as a whole, and step (c) in particular, is energy-efficient,since the strong basicity of a sodium base serves as the driving forceto regenerate said basic anion exchanger for reuse, while eluting MSG insolution in relatively pure form, from which solution it can be readilycrystallized in pure form.

Preferably, said sodium base is selected from the group consisting ofsodium hydroxide, sodium carbonate and sodium bicarbonate, and inespecially preferred embodiments of the present invention, there isprovided a process for the preparation of monosodium glutamate from afermentatively-prepared solution containing monoammonium glutamate, saidprocess comprising (a) contacting said solution containing monoammoniumglutamate salt with a basic anion exchange resin of at least mediumstrength in the hydroxide form to split said salt, whereby saidglutamate attaches to said anion exchanger and ammonia is released insaid solution; (b) subjecting said ammonia-containing solution todistillation, to recover volatile ammonia therefrom; (c) contacting saidglutamate-containing anion exchange resin with a sodium hydroxidesolution to regenerate said strong base anion exchanger and to directlyform monosodium glutamate salt in solution; and (d) crystallizingmonosodium glutamate salt directly from said monosodiumglutamate-containing solution, wherein said crystallized salt has apurity of at least 98%.

Medium strength resins, such as Rohm and Haas' Amberlite IPA 67 andDuolite 374, Purolite's A 830, A 835 and A 845, Mitsubishi's Diaion 11and Beyer's Lewatit S5428, are capable of partial splitting of ammoniumglutamate. As the splitting progresses, the amount of ammonia releasedincreases, and higher pH values are reached in the solution. Tertiaryamine-based anion exchangers, however, lose their binding capacity athigh pH. For completing the splitting of the salt (pH of about 12 orhigher), a strongly basic anion exchanger is preferred. That isparticularly true if Na⁺ and K⁺ are present as contaminants in thefermentation liquor. Suitable strongly basic anion exchangers arequaternary amine-based resins in their OH form, such as Amberlite 900,Amberlite 910, Duolite A1715, IRA 420 and Dow XUS-40196.00.

Therefore, a quaternary amine, strongly basic anion exchanger can beused as the sole salt-splitting anion exchanger in the system. It wasfound, however, that a combination of a weaker anion exchanger having anapparent pKa of at least 9, and a stronger anion exchanger, such as aquaternary amine strongly basic anion exchanger, is especiallypreferred.

Thus, in a preferred embodiment of the present invention, themonoammonium glutamate solution is contacted first with a mediumstrength basic anion exchanger to split a part of the salt, attach partof the glutamate, and release part of the ammonia. The effluent fromthis contact is then contacted with a more strongly basic quaternaryamine anion exchanger for further splitting of the salt, attachment ofglutamate, and release of ammonia. The ammonia-containing effluent fromthis contact, which is substantially free of glutamate, is subjected todistillation for recovery of volatile ammonia therefrom. Theregenerating sodium base solution is contacted first with the quaternaryamine basic anion exchanger and regenerates it. The effluent solution,containing the base and MSG or disodium glutamate, is used to regeneratethe medium strength anion exchanger and to directly form monosodiumglutamate salt in the solution.

The combination of a medium strength anion exchanger and a quaternaryamine basic anion exchanger provides for practically complete glutamaterecovery on the one hand, and regeneration without resorting to highover-all excess of sodium base on the other hand. The amount of sodiumbase introduced into the contact with the glutamate-containing,quaternary amine basic anion exchanger is equivalent to the glutamateattached to that resin plus that attached to the weaker resin.Therefore, there is high excess of sodium base in the contact with thequaternary amine basic anion exchanger, providing for highly efficientelution. The partially neutralized solution formed is used for theregeneration of the weaker anion exchanger, where a marked excess ofbase is not required. This scheme of operation is particularlyadvantageous when the salt splitting (step a) and the regeneration (stepc) are performed in a counter-current flow. On the other hand, when Na⁺and K⁺ contaminants are pre-removed before contact of the monoammoniumglutamate solution with the basic anion exchanger, or when initial fullrecovery of glutamate values is not required, then a basic anionexchanger of medium strength can be used as the sole anion exchanger inthe system.

A quite pure MSG solution is obtained in step (c). Yet some impuritiesmay not be avoided in industrial operation, particularly if saidfermentatively-prepared ammonium glutamate solution is highlycontaminated. The crystallization in step (d) provides for the finalpurification. A bleed of mother liquor is required for removingimpurities. This bleed contains just a small fraction of the glutamate,but still deserves a treatment for recovery of the glutamate valuestherefrom. There are several options for such treatment. The preferredoption will be determined by the nature and content of impurities. Ahighly contaminated bleed can be treated through acidulation. Lesscontaminated bleeds can be sent upstream. Thus, e.g., said bleed can beused as a washing solution in ultrafiltration, or combined with thesolution fed to step (a).

Due to the relative purity of said solution in preferred embodiments ofthe present invention, a part of the mother liquor remaining after thecrystallization of MSG in step (d) can be combined with sodium hydroxidefor use in step (c).

In especially preferred embodiments of the present invention, a part ofthe mother liquor remaining after crystallization of MSG in step (d) iscombined with sodium hydroxide and filtered, prior to being used in step(c).

As will be understood, said fermentative preparation is of the typeinvolving the consumption of carbohydrates and ammonia, and preferablyincludes a step of ultrafiltration to remove cells and other matter fromthe solution containing monoammonium glutamate before contact with saidanion exchanger. Partial concentration of the solution after cellremoval (e.g., via water distillation or reverse osmosis) is optional.

It is also possible to use the first step of the process of U.S. Pat.No. 3,655,746 as a pre-treatment step to remove anionic impuritiesbefore carrying out step (a) of the present invention. Alternatively, orin addition, active carbon, adsorbing resins, or ultra- ornano-filtration can be used for such pretreatment.

In accordance with another embodiment of the present invention, thecontacting of the monoammonium glutamate with the anion exchange resinin step (a) is conducted under CO₂ pressure and the ammonia released inthe solution is at least partially converted to ammonium carbonate.

In accordance with another aspect of the present invention, at least apart of the ammonia released in step (a) is distilled during thecontacting of the monoammonium glutamate solution with the anionexchangers.

In accordance with yet another aspect of the present invention, at leastpart of the solution obtained in step (b) is contacted again with thebasic anion exchanger.

While the invention will now be described in connection with certainpreferred embodiments in the following examples so that aspects thereofmay be more fully understood and appreciated, it is not intended tolimit the invention to these particular embodiments. On the contrary, itis intended to cover all alternatives, modifications and equivalents asmay be included within the scope of the invention as defined by theappended claims. Thus, the following examples which include preferredembodiments will serve to illustrate the practice of this invention, itbeing understood that the particulars shown are by way of example andfor purposes of illustrative discussion of preferred embodiments of thepresent invention only and are presented in the cause of providing whatis believed to be the most useful and readily understood description offormulation procedures as well as of the principles and conceptualaspects of the invention.

EXAMPLE 1

A fermentation broth with concentrations of 120 g/l of glutamic acid; 11g/l of ammonium nitrogen and 16.9 g/l of organic nitrogen, was producedby fermentation of a beet molasses medium mixed with starch hydrolysate.

This solution was contaminated with sugars, due to incompletefermentation; other non-fermentables; inorganic anions and cationsresulting from the molasses, and from nutrients added to thefermentation; and with other fermentation products, such as carboxylicacids.

The bacteria cells and other suspended matter were removed by usingultrafiltration, and were washed by diafiltration with water. In thepermeate, 99% of the glutamic acid of the initial broth was recovered.

Concentrations in the permeate were as follows: 95 g/l of glutamic acid;8.7 g/l of ammonium nitrogen; 11.17 g/l of organic nitrogen. Thetransmittance of the permeate, measured at 750 nm, was 46%.

The above-described permeate was used in all of the examples includedherein.

In Example 1, 4 liters of permeate were fed on a column of 1 liter ofstrong base resin exchanger IPA420 produced by Rohn & Haas, which is atype 1 quaternary amine in OH form. The column was washed with 2 litersof water, was then eluted with 3 liters of caustic soda solution (40 g/lof NaOH), and washed again with 2 liters of water. The glutamic acid andorganic nitrogen were analysed in the eluate plus washing water. 30 g ofglutamic acid and 4 g of organic nitrogen were measured in the eluateplus washing water.

The experiment was repeated, using IRA910 resin, which is also producedby Rohm & Haas, and is a type 2 quaternary amine, instead of IRA420. 32g of glutamic acid and 5.5 g of organic nitrogen were measured in theeluate plus washing water.

EXAMPLE 2

10 liters of permeate were fed on a column of 1 liter of XE583 tertiaryamine resin, which is produced by Rohm and Haas and is a tertiary amine,followed by 2 liters of washing water. The transmittance of theeffluent, measured at 750 nm, was 87%, compared to 46% measured in thepermeate.

5 liters of this effluent was fed on a 1 liter IRA420 OH form column.The column was washed with 2 liters of water and then eluted with 2liters of caustic soda solution (80 g/l NaOH) and 2 liters of water.

70 g of glutamic acid and 6.7 g of organic nitrogen were measured in theeluate plus washing water.

On a second part of the XE583 treated effluent, a tertiary amine resinIRA67, produced by Rohm & Haas and having a pKa of 9.5, was used. Fiveliters of the effluent was fed on a 1 liter IRA67 column; the column waswashed with 2 liters of water and then eluted with 2 liters of causticsoda solution (40 g/l NaOH) and 2 liters of water.

87 g of glutamic acid and 9 g of organic nitrogen were measured in theeluate plus washing water.

EXAMPLE 3

20 liters of the permeate were fed on a column of 1 liter of XE583tertiary amine resin, followed by 2 liters of washing water. Thetransmittance of the effluent, measured at 750 nm, was 81%, compared to46% measured in the permeate.

11.47 g of organic nitrogen was measured for 100 g of glutamic acid inthe effluent. 10 liters of the effluent were fed on a 1 liter column ofgranular active carbon at 65° C. 11.2 g of organic nitrogen for 100 g ofglutamic acid was measured in the effluent of the granular active carboncolumn.

5 liters of this effluent was fed on a 1 liter EXA36 primary amine resincolumn, produced by Mitsubishi Kasei. 10.9 g of organic nitrogen wasmeasured for 100 g of glutamic acid in the effluent of the EXA column.

This last effluent was fed on a column of 1 liter IRA67 resin and 2liters of washing water. The first fraction of effluent was distilled torecover the released ammonia. Virtually all the released ammonia wasrecovered on adding 0.5 g/l NaOH to the effluent.

The resin column was eluted with 2 liters of caustic soda (40 g/l NaOH).10.2 g of organic nitrogen was measured for 100 g of glutamic acid inthe eluate.

Examples 1-3 used large volumes of ultra-filtered fermentation broth tosimulate the resin loading in a counter-current mode of operation. Thisoperation scheme concentrates on the resin some impurities that ingeneral operation are removed in the pre-treatment. The eluate is thusmore contaminated than would be in actual practice. Yet it provides forrecovering most of the MSG in a pure form through crystallization, asshown below in Example 4.

EXAMPLE 4

Example 3 was repeated, using IRA420 resin instead of IRA67. The IRA420column was eluted with caustic soda (80 g/l NaOH).

A fraction of the eluate (pH=8) was neutralized with a small amount ofpure glutamic acid to pH 7.2, concentrated by evaporation under reducedpressure at 60° C., and then cooled at 20° C. Most of the MSGcrystallized at a nitrogen purity of 99%. The purity measured bypolarization was higher than 98%.

EXAMPLE 5

Several weak and medium strength anion exchangers (none of them is astrong base quaternary amine) were compared by equilibration withsolutions comprising ammonium glutamate or its mixtures with ammonia(the mixtures represent solutions after partial salt splitting). Inequilibrium with ammonium glutamate solutions (the resin to aqueoussolution volume ratio was small so that the salt splitting was small),the glutamate loading (equivalents per liter resin) were, in decreasingorder:

    ______________________________________    Amberlite IRA 67 (Rohm and Haas)                          1.5    A 845 and A 830 (Purolite)                          1.35    Diaion WA 11 (Mitsubishi)                          1.0    Duolite A 374 (Rohm and Haas)                          0.9    Diaion WA 30 (Mitsubishi)                          0.5    ______________________________________

The above sequence indicates the sequence of resin capacity at the exitof a counter-current contact with many contact stages. It does notteach, however, the efficiency of salt splitting. For that purpose, theloading in contact with a solution representing partial salt splittingwas determined. In equilibrium with a solution of pH=9 (representing 25%salt splitting), the loadings (eq/l) were:

    ______________________________________    IRA 67, A 845, A 830   about 0.4    WA 11 and A 374        about 0.2    WA 30                  <0.05    ______________________________________

These results could be interpreted to show that the apparent basicity interms of pKa for WA 30 is lower than 9; for WA 11 and A 374 it isslightly higher than 9; and that for IRA 67, A 845 and A 830 it issignificantly higher than 9. Additional equilibrations with solutions,representing salt splitting of 50-90%, show that at this range A 830acts as the strongest resin among these medium strength resins.

EXAMPLE 6

Splitting of ammonium glutamate was tested on a continuouscounter-current contacting with an anion exchanger of a medium strength.

The concentration of the glutamate salt in the solution was 0.8 eq/l.The resin was Purolite's A 830, described by the manufacturer as amacroporous, weak base acrylic resin, obtained and used in the free baseform. The glutamate-carrying resin was eluted with an NaOH solution andsent back to contact the glutamate solution. The resin loading, in termsof equivalents of glutamate bound per liter resin, and the efficiency ofsalt splitting (the fraction of glutamate in the incoming solution thatwas bound to the resin) were determined. The flow rates in terms ofsolution volume per resin volume ranged between 0.7 and 2.4. For theseflow rates, the resin loading ranged between 0.49 and 0.76 eq/lrespectively, and the salt splitting between 86 and 39% respectively.Thus, at flow rate of 1.2, the resin loading was 0.63 eq/l and the saltsplitting effiency was 66%. These results show that, using the mediumstrength anion exchanger, Purolite A 830, high salt splitting yields andgood anion exchange capacity are obtainable.

EXAMPLE 7

The experiment of Example 6 was repeated, using Rohm and Haas' AmberliteIRA 67, described by the manufacturer as a macroreticular, weak baseacrylic resin, obtained and used in the free base form. The flow ratesrange was 0.7 to 2.6. The loading ranged between 0.4 and 0.9 eq/lrespectively, and the salt splitting efficiencies ranged between 70 and40% respectively. At a flow rate of 1.6, the resin loading and theefficiency were 0.7 and 55% respectively. These results show that, usingthe medium strength anion exchanger Amberlite IRA 67, high saltsplitting yields and good anion exchange capacity are attainable.

EXAMPLE 8

The experiments in Examples 6 and 7 were repeated, with two changes:

1) the feed was a solution comprising 0.25 eq/l ammonium glutamate and0.5 eq/l ammonia, representing an ammonium glutamate solution after 67%salt splitting on a medium strength anion exchanger) and

2) the resin was a styrinic strong base anion exchanger, Rohm and Haas'Amberlite IRA 900.

At feed rates of 2.85 and 3.24, loadings of 0.71 and 0.81 eq/l werefound. Glutamate adsorption from the solution is practically completed.

EXAMPLE 9

20 liters of the permeate were pretreated as in Example 3, using XE583tertiary amine resin, granular active carbon and then EXA36 primaryamine resin. The last effluent out of EXA36 resin was fed on a IRA67column and its effluent on a IRA420 colum. Thereafter, water was fed forsweetening of the two colums. A total of 735 g of glutamic acid wasloaded on the two columns, 400 g on the IRA67 and 335 g on the IRA420,measurement being effected on a sample of resin. The two columns werethen eluted by 2.25 1 of 80 g/l caustic soda solution, fed first on theIRA420 column, the effluent of which was then fed on the IRA67 column.Thereafter, water was fed for sweetening of the two columns. The finaleffluent, having a pH of 7.3, was concentrated by evaporation underreduced pressure at 65° C. for MSG crystallization. Crystallized MSG wasseparated from crystallization mother liquor and dried under vacuum.

350 g of MSG crystal, having a 99.5 purity, were obtained. Measured bypolarization and nitrogen analysis, the crystallization yield was 47%.

It will be evident to those skilled in the art that the invention is notlimited to the details of the foregoing illustrative examples and thatthe present invention may be embodied in other specific forms withoutdeparting from the essential attributes thereof, and it is thereforedesired that the present embodiments and examples be considered in allrespects as illustrative and not restrictive, reference being made tothe appended claims, rather than to the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed is:
 1. A process for the preparation of monosodiumglutamate from a fermentatively-prepared solution containingmonoammonium glutamate, said process comprising:(a) contacting saidsolution containing monoammonium glutamate salt with a basic anionexchange resin having an apparent basicity in the range of pKa of atleast 8 whereby glutamate anions attach to said anion exchanger andammonia is released in said solution; (b) subjecting saidammonia-containing solution to distillation, to recover volatile ammoniatherefrom; (c) contacting said glutamate-containing anion exchange resinwith a sodium base solution to regenerate said basic anion exchanger andto directly form monosodium glutamate salt in solution; and (d)crystallizing monosodium glutamate salt directly from said monosodiumglutamate-containing solution.
 2. A process according to claim 1,wherein said crystallized salt has a purity of at least 98%.
 3. Aprocess according to claim 1, wherein said sodium base is selected fromthe group consisting of sodium hydroxide, sodium carbonate and sodiumbicarbonate.
 4. A process according to claim 1, wherein said sodium baseis sodium hydroxide.
 5. A process according to claim 1, wherein theammonia recovered by said distillation is recycled for the fermentativepreparation of monoammonium glutamate.
 6. A process according to claim1, wherein said fermentative preparation is of the type involving theconsumption of carbohydrates and ammonia.
 7. A process according toclaim 1, wherein mother liquor remaining after the crystallization ofmonosodium glutamate in step (d) is combined with sodium hydroxide foruse in step (c).
 8. A process according to claim 1, wherein motherliquor remaining after crystallization of monosodium glutamate in step(d) is combined with sodium hydroxide and filtered, prior to being usedin step (c).
 9. A process according to claim 1, wherein said solutioncontaining monoammonium glutamate salt is first contacted with a mediumstrength basic anion exchanger to split a part of said salt, attach partof said glutamate anions and release part of said ammonia, and then theeffluent from said contact is contacted with a stronger quaternary aminebasic anion exchanger for further splitting of said salt, attachment ofsaid glutamate anions, and release of ammonia.
 10. A process accordingto claim 9, wherein said ammonia-containing effluent, substantially freeof glutamate anions, is subjected to distillation for recovery ofvolatile ammonia therefrom.
 11. A process according to claim 9, whereinsaid regenerating sodium base solution is first contacted with saidquaternary amine basic anion exchanger to regenerate the same,whereafter the resulting effluent solution is used to regenerate saidmedium strength basic anion exchanger and to directly form monosodiumglutamate salt in said solution.
 12. A process according to claim 1,wherein the contacting of the monoammonium glutamate with the anionexchange resin in step (a) is conducted under CO₂ pressure and theammonia released in said solution is at least partially converted toammonium carbonate.
 13. A process according to claim 1, wherein at leasta part of the ammonia released in step (a) is distilled during thecontacting of the monoammonium glutamate solution with the anionexchangers.
 14. A process according to claim 1, wherein at least part ofthe solution obtained in step (b) is contacted again with the basicanion exchanger.
 15. A process according to claim 1, wherein contactinga solution comprising ammonium glutamate or a sodium base solution withthe resin is conducted counter-currently.
 16. A process according toclaim 1, wherein said basic anion exchange resin has an apparentbasicity in the range of pKa of at least
 9. 17. A process according toclaim 2, wherein said crystallized salt has a purity of at least 99%.